Lens and projection headlight of a motor vehicle including same

ABSTRACT

The plano-convex lens of a projection headlight has a holding edge ( 4 ) integrally formed on an outer lens edge and a supporting edge ( 5 ) projecting from its plane surface ( 3 ) and formed integrally with the holding edge ( 4 ). The supporting edge ( 5 ) and the holding edge ( 4 ) form a continuous cylindrical outer circumferential surface ( 45 ) extending over their outer sides. The convex surface ( 2 ) and the plane surface ( 3 ) of the lens are bright pressed surfaces so that the grinding and polishing steps usually used in making the lens can be eliminated. The method of manufacturing the lens including bright pressing the convex and plane surfaces is also part of the invention.

BACKGROUND OF THE INVENTION

The invention relates to a lens having a curved surface and a planesurface on opposite sides, and a holding edge molded on the lens edge aswell as a supporting edge projecting from the plane surface and moldedon the holding edge, to use of the lens and to a method of manufactureof the lens.

J59-177506A describes lenses of a projection objective wherein the twoexternal lenses of the objective have a supporting edge which projectstowards the plane lens surface and is designed as stepped. The shoulderthereby produced is used for support on a further lens, namely abiconvex lens, with the aim of specifying a distance between the lenses.

JP59-157603A shows two lenses which have supporting edges havingprojections with inclined surfaces provided on their outercircumference. As a result of this configuration, importance is placedon high precision and stability of the edges.

In this respect, the supporting edges in both of the foregoing citedprior art references are designed and constructed according to theirmounting configuration with further lenses.

Such lenses have conventionally been pressed into an aspherical shape onone side and subjected to a grinding process to form a plane surface onthe other side. This grinding process, which is followed by anotherpolishing process, is carried out after passage through a coolingfurnace. The passage through a cooling furnace is necessary tospecifically cool the still hot blank so that stresses inside the lenscan be removed. In this case, however, the blank must be placed on aconveyer belts, whereby the supporting surface of the lens isdisadvantageously influenced. However, if the passage through thecooling furnace is followed by a grinding process, these surfacedeformations are eliminated.

However, this method has the disadvantage that additional grinding andpolishing processes are required.

SUMMARY OF THE INVENTION

The object of the invention is to provide a lens and a method ofmanufacture in which such a finishing process such as grinding andpolishing is dispensed with. The object also relates to thespecification of a particular use.

This object is solved by a lens which is pressed bright on both sides.As a result of said bright pressing on both sides, correspondingfinishing processes are dispensed with. Said bright pressing is therebypossible because a supporting edge is present which has the advantagethat when placed on a base, the lens abuts exclusively with thissupporting edge and contact of the plane surface and the base is avoidedso that the plane lens surface is not damaged. A lens pressed bright onboth sides with a supporting edge can thus be placed without anyproblems on a conveyor belt, for example, of a cooling furnace.

The supporting edge is preferably molded onto the outer circumference ofthe lens. Since the holding edge is molded on the outer circumferentialedge of the lens and the supporting edge is molded on this holding edge,the supporting edge is located outside the ray path and thus outside theoptically active surface of the lens.

The thickness D of the supporting edge is at least 0.2 mm. This minimumthickness is required so that any unevenness on the supporting surface,especially on a cooling belt, does not lead to any contact with theplane surface.

The width B₁ of the supporting edge is preferably less than or equal tothe width B₂ of the holding edge.

Preferably, a lens pressed bright on both sides comprising a curvedsurface, a plane surface and a holding edge molded on the lens edges, onwhich is molded a supporting edge projecting or protruding from theplane surface, is used for projection headlights for motor vehicles.

The method for the manufacture of a lens comprising a curved surface anda plane surface provides that a holding edge is molded on the lens edgeand a supporting edge which protrudes from the plane surface is moldedon the holding edge and that both surfaces are pressed bright.

The lens is preferably placed on the supporting edge during the coolingprocess.

BRIEF DESCRIPTION OF THE DRAWINGS

An exemplary embodiment of the invention is described in detail belowwith reference to the drawings.

In the figures,

FIG. 1 is a cross-sectional view through a plano-convex lens accordingto the invention, which is resting on a base via its supporting edge;and

FIG. 2 is a cross-sectional view through a part of a projectionheadlight with the lens in the built-in state.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a cross-sectional view of the plano-convex lens 1 accordingto the invention. The plano-convex lens has an aspherical convex surface2 and a plane surface 3. Molded onto the outer edge of the lens 1 is aholding edge 4, which in its outer region goes over into a supportingedge 5 which projects from the plane surface 3. The lens is supported ona base 6 only by means of the supporting edge 5 so that the plane lenssurface 3 cannot be damaged. The supporting edge 5 projects from thesurface 3 by its thickness D of around 0.3 mm. The width B₁ of thesupporting edge 5 is less than the width B₂ of the holding edge 4,measured in a direction parallel to the plane lens surface 3, so thatthe optically active area of the plane surface 3 is not restricted. Ifthe glass lens 1 is pressed bright on both sides, it can be stored andtransported without any problems after the bright pressing process or itcan be supplied to further process steps with regard to cooling withoutthe lens surface being damaged thereby.

The supporting edge 5 and holding edge 4 together from a continouscylindrical outer circumferential surface 45 of the lens, which extendsover an outer side of both the supporting edge 5 and the holding edge 4as well as around an outer circumference of the lens. The supportingedge 5 of the lens is not set back or set in from the outer peripheraledge of the lens in the preferred embodiment shown in FIG. 1.

FIG. 2 shows the plano-convex lens 1 in the built-in state in projectionheadlight of a vehicle. A holder 10 embraces the holding edge 4 on itsside facing the convex surface 2 of the plano-convex lens 1. The holder10 substantially consists of a sheet-metal ring having flaps 12 stampedout on its circumferential wall 11, which are curved inwards. A circlip13 is arranged between the flaps 12 and the supporting edges 5. By thismeans the lens is securely held. The advantage is that the supportingedge 5 is also used for building the lens into the headlight so that theplane surface 3 is not adversely affected by the holder.

1. A method for making a lens having a curved surface (2) and a planesurface (3) on opposite sides thereof, and having a holding edge (4)integrally formed on a lens edge, wherein a supporting edge (5) projectsfrom said plane surface (3) and is formed integrally with said holdingedge (4), said method comprising bright pressing said curved surface andsaid plane surface on both of said sides.
 2. A plano-convex lens havinga convex surface (2) and a plane surface (3) on opposite sides thereof,and comprising a holding edge (4) and a supporting edge (5), saidholding edge (4) being integrally formed on an outer circumferentialedge of the lens and said supporting edge (5) projecting from said planesurface (3) and being formed integrally with said holding edge (4), andsaid convex surface (2) and said plane surface (3) being bright pressedsurfaces; wherein a lower surface of said holding edge (4) faces awayfrom said convex surface (2) and is disposed in a plane that coincideswith said plane surface (3); and wherein said supporting edge (5) andsaid holding edge (4) form a continuous cylindrical outercircumferential surface (45) extending over an outer side of saidsupporting edge (5) and an outer side of said holding edge (4) andaround an outer circumference of the lens.
 3. The plano-convex lens asdefined in claim 2, wherein said supporting edge (5) has a thickness (D)of at least 0.2 mm.
 4. The plano-convex lens as defined in claim 2,wherein said supporting edge (5) has a width (B₁), said holding edge (4)has a width (B₂) in a direction extending parallel to said plane surface(3) and said width of said supporting edge (5) is less than or equal tosaid width of said holding edge (4).
 5. The plano-convex lens as definedin claim 2, consisting of a glass lens.
 6. A plano-convex lens of aprojection headlight of a motor vehicle, said plano-convex lensconsisting of a glass lens and having a convex surface (2) and a planesurface (3) on opposite sides thereof, said plano-convex lens comprisinga holding edge (4) and a supporting edge (5), said holding edge (4)being integrally formed on an outer circumferential edge of the lens andsaid supporting edge (5) projecting from said plane surface (3) andbeing formed integrally with said holding edge (4), and said convexsurface (2) and said plane surface (3) being bright pressed surfaces. 7.The plano-convex lens as defined in claim 6, wherein said supportingedge (5) has a width (B₁), said holding edge (4) has a width (B₂) in adirection extending parallel to said plane surface (3) and said width ofsaid supporting edge (5) is less than or equal to said width of saidholding edge (4).
 8. A projection headlight of a motor vehicle, saidprojection headlight comprising a plano-convex lens (1) and a holder(10) that holds said plano-convex lens (1), said plano-convex lens (1)having a convex surface (2) and a plane surface (3) on opposite sidesthereof, said plano-convex lens (1) comprising a holding edge (4) and asupporting edge (5), said holding edge (4) being integrally formed on anouter circumferential edge of the lens, said supporting edge (5)projecting from said plane surface (3) and being formed integrally withsaid holding edge (4), said convex surface (2) and said plane surface(3) being bright pressed surfaces, a lower surface of said holding edge(4) facing away from said convex surface (2) and being disposed in aplane that coincides with said plane surface (3), and said supportingedge (5) and said holding edge (4) forming a continuous cylindricalouter circumferential surface (45) that extends over an outer side ofsaid supporting edge (5) and an outer side of said holding edge (4) andaround an outer circumference of the lens; and said holder (10)embracing said holding edge (4) on a side of said lens having saidconvex surface (2), said holder (10) substantially consisting of a sheetmetal ring, said sheet metal ring comprising a circumferential wall(11), said circumferential wall (11) extending circumferentially aroundsaid holding edge (4) and said supporting edge (5), said circumferentialwall (11) bearing on the continuous cylindrical outer circumferentialsurface (45), and said circumferential wall (11) being provided withinwardly curved flaps (12) that are engaged under the supporting edge(5) to securely hold the lens (1) in the holder (10).
 9. The projectionheadlight as defined in claim 8, wherein said supporting edge (5) has awidth (B₁), said holding edge (4) has a width (B₂) in a directionextending parallel to said plane surface (3) and said width of saidsupporting edge (5) is less than or equal to said width of said holdingedge (4).
 10. A projection headlight of a motor vehicle, said projectionheadlight comprising a plano-convex lens (1) and a holder (10) thatholds said plano-convex lens (1), said plano-convex lens (1) consistingof a glass lens and having a convex surface (2) and a plane surface (3)on opposite sides thereof, said plano-convex lens comprising a holdingedge (4) and a supporting edge (5), said holding edge (4) beingintegrally formed on an outer circumferential edge of the lens and saidsupporting edge (5) projecting from said plane surface (3) and beingformed integrally with said holding edge (4), and said convex surface(2) and said plane surface (3) being bright pressed surfaces; and saidholder (10) embracing said holding edge (4) on a side of said lenshaving said convex surface (2), said holder (10) substantiallyconsisting of a sheet metal ring, said sheet metal ring comprising acircumferential wall (11), said circumferential wall (11) extendingcircumferentially around said holding edge (4) and said supporting edge(5), said circumferential wall (11) bearing on a continuous cylindricalouter circumferential surface (45) of said supporting edge (5) and saidholding edge (4), and said circumferential wall (11) being provided withinwardly curved flaps (12) that are engaged under the supporting edge(5) to securely hold the lens (1) in the holder (10).
 11. The projectionheadlight as defined in claim 10, wherein said supporting edge (5) has awidth (B₁), said holding edge (4) has a width (B₂) in a directionextending parallel to said plane surface (3) and said width of saidsupporting edge (5) is less than or equal to said width of said holdingedge (4).